The public purse will have to pay out at least £3m for the operation to combat Northern Ireland's spring blizzard, the Assembly has heard.

Regional Development Minister Danny Kennedy said the total – on top of the £5m compensation scheme already signed off – was an "early estimate" and applied to his department alone.

One-sixth of the salt supply for the entire winter period – the six months from mid-October to mid-April – was used in six days.

And the carcasses of more than 8,300 sheep and cattle have been taken from 440 farms so far.

Mr Kennedy said agencies had co-operated well during the crisis but admitted further talks with councils over responsibilities for clearing footpaths could be useful.

"But it is simply not practical or possible that every single footway and area on every housing estate can be cleared (and) it is unrealistic to raise that expectation," he added. The DUP's Jimmy Spratt, chair of the committee which monitors Mr Kennedy and his department, said many staff had made supreme efforts, often at risk to themselves but asked if there were lessons for the future – including investment in more equipment.

"I have already begun to make the argument to Executive colleagues for the need to invest further in our winter preparation plant, such as snowploughs, etc," Mr Kennedy said.

Mr Kennedy said he had witnessed snow drifts up to 20ft high in the Mournes and Glens of Antrim, "something I have never seen before".

"It took nearly a week to get all areas back to near normality," he told MLAs.

Alliance's Trevor Lunn said he vividly remembered the huge snowfall of 1963 and believed the incident this year was worse. He asked whether the scheme – which involves Department of Regional Development and 23 of the 26 councils – is sufficiently secure and clear in respect of funding and liability.

"I do not discount the fact that we can make further efforts to improve that. Strictly speaking, neither local councils nor, indeed, Roads Service in the Department for Regional Development have a statutory obligation, as it stands, to clear footpaths," Mr Kennedy said.

"Clearly, it is in the public interest and in the interest of the health of our citizens to do that, and there is an expectation that it should happen. However, that has resource implications and perhaps legal implications, too."

But he said he would be happy to engage further with the Northern Ireland Local Government Association and other local government bodies "to see whether we can improve that further".